1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying apparatus or a printer, and more particularly to an improvement in the image forming apparatus provided with a sheet reversing mechanism.
2. Related Background Art
In the conventional image forming apparatus, as shown in FIG. 6, for forming images on both faces of a sheet such as paper, an image forming unit B in the main body 1 of the apparatus is provided with a reversal path 29 for reversing a sheet feeding direction i.e., front/rear face and a forward-reverse rotation roller 32, while a cassette pedestal (paper feeding unit) C is provided with a reversal path 40. A sheet bearing an image on a side thereof is once fed into the reversal path 29 by the forward rotation of the roller, and then the roller is rotated reversely to introduce the reversed sheet into the image forming unit through a convey path 18 whereby another image is formed on the other side of the sheet. A longer sheet can also be reversed by feeding a part thereof into the reversal path 40 in the cassette pedestal.
In such image forming apparatus, however, if an openable guide member supporting the forward-reverse rotation roller is opened to remove the jammed sheet therein, the sheet drops to the reversal path 40, thus remaining in an blocking the path. In such situation, the ensuing sheet entering the reversal path cannot smoothly enter the reversal path and may eventually be creased to cause jamming trouble.
For avoiding such situation, it has been tried to install a sheet sensor inside the reversal path or to employ an openable cover for removing the remaining sheet, but such measures have resulted in a wider space required, an increase in the cost or an increase in the jam removing process. Also the sheet sensor may be unable to detect the sheet which has been broken and has remained in the apparatus. Particularly in case a finisher F containing multiple sheet discharging trays is installed and if a sheet remains in the sheet reversing unit at a sheet jamming, it is necessary to move the finisher F for making a space for opening a door 30, for the purpose of jam elimination in the sheet reversing unit.
Also, even if the main body is used alone without the multiple sheet discharging trays, the sheet reversal is to be conducted within the apparatus because otherwise the sheet to be reversed appears outside the apparatus and may cause danger to the operator. Therefore, if the sheet drops into the reversal path in a sheet jamming, a wide space is likewise required in order to open one side of the sheet guides for eliminating such dropped sheet.